Why feign performs urlencode twice on the query parameter values?

Feign encodes a query string twice that : finally becomes %253A and the correct result should be %3A.

First encoding happens when creating a RequestTemplate (ReflectiveFeign.java:213) RequestTemplate template = resolve(argv, mutable, varBuilder);

Second encoding happens when constructing a Request (SynchronousMethodHandler.java:88) Request request = targetRequest(template);

Though one of the RequestTemplate’s query() methods accepts a boolean parameter to determine whether to encode the query parameter values, the default value of this boolean is false and there is no way to change its value.

Finally, I have to write a RequestInterceptor to decode the query parameter values between the two encodings.

Why would feign do two encodings on query parameter values? Is it a bug or did I miss something?

[ryeyao]

@kgym here is my quick workaround (ugly but works)：

@Component
public class FeignMonitorRequestInterceptor implements RequestInterceptor {
    private static String urlDecode(String arg) {
        try {
            return URLDecoder.decode(arg, Util.UTF_8.name());
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void apply(RequestTemplate template) {
        
        for (String key : template.queries().keySet()) {
            Collection<String> values = template.queries().get(key);
            if (allValuesAreNull(values)) {
                continue;
            } else {
                Collection<String> encodedValues = new ArrayList<String>();
                for (String value : values) {
                    encodedValues.add(urlDecode(value));
                }
                template.query(true, key, encodedValues);
            }
        }
    }

    private boolean allValuesAreNull(Collection<String> values) {
        if (values == null || values.isEmpty()) {
            return true;
        }
        for (String val : values) {
            if (val != null) {
                return false;
            }
        }
        return true;
    }
}

[kdavisk6]

Duplicate of #662